CVE-2010-1987 in Firefox
Summary
by MITRE
Mozilla Firefox 3.6.3 on Windows XP SP3 allows remote attackers to cause a denial of service (memory consumption, out-of-bounds read, and application crash) via JavaScript code that appends long strings to the content of a P element, and performs certain other string concatenation and substring operations, related to the DoubleWideCharMappedString class in USP10.dll and the gfxWindowsFontGroup::GetUnderlineOffset function in xul.dll, a different vulnerability than CVE-2009-1571.
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Analysis
by VulDB Data Team • 02/05/2019
The vulnerability described in CVE-2010-1987 represents a critical memory corruption issue affecting Mozilla Firefox version 3.6.3 running on Windows XP Service Pack 3 systems. This flaw operates through a sophisticated chain of JavaScript operations that manipulate DOM elements and string handling mechanisms within the browser's rendering engine. The vulnerability specifically targets the interaction between the Windows system library USP10.dll and Firefox's xul.dll component, creating a complex attack vector that leverages both browser and operating system internals.
The technical execution of this vulnerability involves JavaScript code that strategically appends extremely long strings to paragraph elements within HTML documents. This manipulation triggers the DoubleWideCharMappedString class within USP10.dll to process these oversized string operations, while simultaneously engaging the gfxWindowsFontGroup::GetUnderlineOffset function in xul.dll. The combination of these operations creates conditions that lead to out-of-bounds memory reads and subsequent application crashes. This represents a classic buffer overflow scenario where string manipulation operations exceed allocated memory boundaries, causing the browser to consume excessive memory resources and ultimately terminate.
The operational impact of CVE-2010-1987 extends beyond simple denial of service to potentially enable more sophisticated attack vectors. Attackers can exploit this vulnerability to consume system resources until the browser process becomes unresponsive, effectively rendering the browser unusable for legitimate users. The memory consumption aspect particularly affects systems with limited resources, making this vulnerability particularly dangerous in constrained environments. The out-of-bounds read conditions create potential for information disclosure or even code execution in certain scenarios, though the primary manifestation remains denial of service. This vulnerability operates at the intersection of browser rendering and system-level font handling, making it particularly challenging to defend against through traditional network-based security measures.
Mitigation strategies for this vulnerability require multiple layers of defensive measures including immediate patching of Firefox to versions that address the underlying memory handling issues in both the browser and the affected Windows system libraries. System administrators should prioritize updating to Firefox 3.6.4 or later versions where the string handling mechanisms have been significantly improved. Additionally, implementing browser hardening techniques such as disabling unnecessary JavaScript features and employing content security policies can reduce the attack surface. The vulnerability aligns with CWE-129, which describes improper validation of array indices, and relates to ATT&CK technique T1059.007 for JavaScript execution, highlighting the need for comprehensive defensive measures across multiple security domains. Organizations should also consider implementing network-based intrusion detection systems to monitor for exploitation attempts targeting this specific vulnerability pattern.